Objective: To evaluate the effectiveness of interventions for treating functional dysphonia or preventing voice disorders in adults.
Data sources: We searched MEDLINE (1950 to 2006), EMBASE (1974 to 2006), CENTRAL (Issue 2 2006), CINAHL (1983 to 2006), PsychINFO (1967 to 2006), Science Citation Index (1986 to 2006), and the Occupational Health databases OSH-ROM (February 2006).
Review methods: Systematic review and meta-analysis of randomized controlled trials. Included studies evaluated the effectiveness of interventions for 1) treating functional/nonorganic dysphonia or 2) preventing voice disorders. We identified six randomized controlled trials about treatment and two about prevention. Two authors independently extracted data and assessed trial quality.
Results: A combination of direct and indirect voice therapy, compared with no intervention, improves self-reported (standardized mean difference -1.07; 95% CI -1.94 to -0.19), observer-rated (weighted mean difference [WMD] -13.00; 95% CI -17.92 to -8.08), and instrumentally assessed vocal functioning (WMD -1.20; 95% CI -2.37 to -0.03) in adults with functional dysphonia. Effects are reported to remain for at least 14 weeks. Effects are similar in patients and in teachers and student teachers screened for voice problems. We found two studies that did not show voice training, compared with no intervention, to have a preventive effective in improving self-reported vocal functioning. Assessment of publication bias showed that the real effect sizes are probably smaller.
Conclusion: Comprehensive voice therapy is effective in improving vocal performance in adults with functional dysphonia. There is no evidence of effectiveness of voice training in preventing voice disorders.